The present invention relates to a method for fabricating an integrated coil-on-keeper assembly.
The density of concentric data tracks on magnetic discs continues to increase (that is, the width of data tracks and radial spacing between data tracks are decreasing), requiring more precise radial positioning of the head. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuation motor, such as a voice coil motor, to radially position a slider (which carries the head) on a flexure at the end of the actuator arm. The large-scale motor lacks sufficient resolution to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism, or microactuator, is necessary to accommodate the more densely spaced tracks.
One particular design for high resolution head positioning involves employing a high resolution microactuator in addition to the conventional lower resolution actuator motor, thereby effecting head positioning through dual stage actuation. Various microactuator designs have been considered to accomplish high resolution head positioning. In particular, magnetic microactuator designs featuring a magnet/keeper assembly and coil have been developed. Magnetic microactuators typically include a stator portion and a rotor portion, the stator being attached to the flexure and the rotor supporting the slider. The rotor is movable with respect to the stator such that the slider can be positioned more precisely over a track of a disc.
The components that make up a magnetic microactuator can be numerous. Typically, such components include a micromachined stator/rotor element, a conductive drive coil, a conductive sense coil, a permanent magnet, a keeper layer to contain the magnetic field and insulator layers. The cost of manufacturing and assembling these separate components into a single microactuator can be prohibitive. Furthermore, establishing a fully integrated process with all these components is not actively feasible due to process limitations, the geometry of the device, contamination concerns or chemical incompatibility. An assembly for use in a magnetic microactuator with coil and keeper components can be found in U.S. patent application Ser. No. 09/490,421, filed Jan. 24, 2000, by Crane et al., entitled xe2x80x9cCoil Structures for Magnetic Microactuatorxe2x80x9d and is hereby incorporated by reference. Some components of the microactuator can be integrated into an assembly in a single process and are the subject of the present invention. There is a need in the art for a method of fabricating an integrated assembly comprised of the keeper, the coils and the insulator components of the microactuator, particularly a fabrication method that is cost efficient and produces the assemblies in bulk.
The present invention is a method for fabricating an integrated coil-on-keeper assembly for use with a magnetic circuit in a microactuator. The method includes forming a keeper substrate and forming a top insulator layer upon the keeper substrate. A coil layer is formed on top of the top insulator layer and the keeper substrate. A bottom insulator layer is formed upon the coil layer and the keeper substrate is etched to form a top keeper. A plurality of coil-on-keeper assemblies are formed in one process on a single keeper substrate and then singulated after etching the top keeper. During fabrication a singulation via is formed around each coil-on-keeper assembly formed on the keeper substrate. A temporary support is formed within each singulation via and around each individual coil-on-keeper assembly prior to etching the top keeper. The temporary support holds each assembly on the keeper substrate during etching of the top keeper.
Coil-on-keeper assemblies are also fabricated with a drive coil layer and a sense coil layer. A middle insulator layer is formed between the two coil layers to encapsulate each coil layer. In each coil-on-keeper assembly, portions of each coil layer are exposed through electrical vias in the top insulator layer. Solder pads can be connected at these points where the coil layers are exposed to provide electrical contacts with the coils.